Plastic products, such as automotive bumpers and so forth, are produced by injection molding. The injection molding is effected by injecting a thermoplastic resin into a cavity of a closed mold. When a change is made in the type of products, the mold is also changed. According to a conventional practice, the mold is replaced by directly bringing a new mold by a forklift truck into a clamping mechanism of an injection molding machine every time the mold is changed.
An automatic mold mounting technique of the prior art in Japan has been disclosed in Laid-Open Japanese Patent Application No. 63-159026 (Japanese Patent Application No. 61-306213 filed Dec. 24, 1986).
In Laid-Open Japanese Patent Application No. 63-159026 is disclosed an automatic mold mounting apparatus having a mold carrying means designed to carry the mold into a mold plate from a mold carrier for carrying the mold to a molding machine, a means for judging the type of a mold moving into the mold plate, and a control means for stopping the movement of the mold that has been judged as a different type of mold.
Bumpers differ in shape with types of motor vehicles. A plurality of molding machines, therefore, are juxtaposed to perform the molding of a plurality of types of bumpers. According to this conventional layout of molding machines, it is necessary to drive a forklift truck in a wide range of movement to change the mold every time mold replacement is demanded, resulting in a very low operation efficiency. Moreover, it is necessary to provide wide space to allow the movement of the forklift truck to each molding machine and sufficient room for mold replacement. And naturally a large space is allotted for the molding process.